Controllable energy dissipator



Aug 27, 1940.r Y T. M. GLUYAS, JR 2,213,104

QONTROLLABLE ENERGY DISSIPATOR Y Filed Hafen 15,- 1939 I 2 sheets-sheet1 To Antenna.

dmrier Aug. 27, 1940.

T. M. GLUYAs. JR 2,213,104 CONTROLLABLE ENERGY DISSIPATOR Filed March15, 1939 2 Sheets-Sheet 2 Patented Aug. 27, 1940 UNITED STATEScoNTRoLLABLE ENERGY DIssIPA'roa Thomas M. Gluyas, Jr., Kansas City, Mo.,assignor, by mesne assignments, to Pennsylvania Patents, Inc., CarsonCity, Nev., a corporation of Nevada Application March 15, 1939, SerialNo. 262,042

11 Claims.

This invention relates to a method of and means for forming acontrollable dissipating means for electrical energy. It is particularlyapplicable to a system such as that disclosed and claimed in thecopending application of William N. Parker, Serial No. 84,534, filedJune 10, 1936. rThe said Parker application discloses a modulatingsystem which is particularly useful in the generation of a modulatedhigh frequency carrier signal for television where a wide band offrequencies must be transmitted for satisfactory picture reproduction.In that application, there are provided means for accomplishingmodulation at a high level and with considerably greater efficiency, aswell as for a wide band of frequencies. The principal feature of theParker system resideslin shunting a high impedance source of carrierfrequency energy by a variable' energy dir ssipating impedance which iscontrollable in response to the modulating signal` In order that thesystem shall function with maximum efficiency and be capable of yieldingone hundred per cent modulation of the carrier wave, it is desirablethat this impedance shall be reducible to zero for a particular value ofthe modulating signal. The Parker application provides means forobtaining such an impedance by inverting the impedance of one or morevacuum tubes. The plate impedance of these tubes can readily be madesubstantially infinite by applying a suificiently negative controlvoltage to the grids, althoughit cannot be made to approach zero veryclosely by applying even a large positive voltage. However, by invertingthe tube impedances through quarter wave-length transmission lines orequivalent means, an impedance is obtained which can be varied from zeroto a very large value according to the amplitude of the control signal,applied to the grids of the tubes.

With such a system, the current drawn by the modulating impedance fromthe carrier source is zero for peaks of modulation and a maximum forvalleys, while for carrier level the current drawn by the modulatingimpedance is equal to that drawn by the antenna or other useful load.Accordingly, the energy dissipation of the modulating impedance is zerofor peaks and valleys of modulation and is equal to that of the antennaat carrier level. In order that this may obtain,

it renews that the tubes which make up the energy dissipating modulatingimpedance must draw maximum current for peaks, half maximum for carrierlevel, and zero current for valleys of modulation.

5 The object of the present invention is to provide a modulatingimpedance in which the energy dissipating tube operates over a differentportion of its plate current-grid voltage characteristic, whereby thecurrent drawn by the tubes over the modulation cycle varies to a lesserextent than in the Parker system. From one point of View, the modulatingimpedance of the present invention may be regarded as a modification ofthat of the Parker system in which modification the energy-dissipatingtubes are inserted in the 10 middle of the quarter-waveimpedance-inverting transmission line. The rate at which they dissipateenergy is controlled by applying the modulating signal through tubesplaced in the same position as the modulating tubes in the Parker systembut which dissipate comparatively little energy. The mode of operationof the invention will more readily be understood by reference to thefollowing description and the accompanying drawings in which: 2(

Fig. 1 is a diagram of a modulating system embodying one form ofmodulating impedance according to the invention.

Figs. lA'and 1B are explanatory diagrams which will be referred to indescribing the invention; 25

Fig. 2 is a diagram of a modulating system employing another embodimentof a modulating impedance according to the method of the invention.

Referring rst to Fig. l, there is shown a modu- 30 lating system whichresembles in many respects that disclosed in the aforementioned Parkerapplication. The carrier signal from the source I is applied to the gridofthe tube 2, the plate of which is coupled to the transmission line 3func- 35 tioning in the capacity of a tank circuit. The line may betuned by means of the shorting disc 4 so that its effective electricallength, as modied by the output capacity of the tube 2, is equal to aquarter wave-length of the carrier frequency 40 signal. Plate voltagemay be supplied to the tube 2v by means of the connection 5 to thetransmission line as shown. Carrier power is derived from the tankcircuit at a point 6 near the end l of the line 3, whereby the tankcircuit presents a 45 low impedance to the transmission line 1 whichsupplies the power to the load point B. Line 'l may be a quarter-waveline, or one having an electrical length equal to an old number ofonequarter wave lengths at the carrier frequency, 50 for the purpose ofinverting lthe low impedance of the tank circuit to form a highimpedance source at the point 8. Power may be supplied from the loadpoint to an antenna or other signal utilization means through atransmission line 9, as

shown, or by other suitable means. It will be noted that the lines shownare coaxial and their outer conductors may be grounded as is commonpractice in the art; however, the use of coaxial lines is not anessential feature of the invention, and open wire lines may be usedwhere convenient. Coupling condensers are also used where necessary torestrict D. C. to those portions of the circuit in which it is desired.

That portion of the system of Fig. l which has so far been described isidentical in function to the Parker system. Considering now themodulating impedance, it will be seen to consist essentially of the twoone-eighth wave-length lines Ill and II, the energy-dissipating tube I2inserted between them, and the control tube I3 to the grid of which issupplied the modulating signal from the source em. It has already beenobserved that most of the energy dissipated in the process of modulationis absorbed in the tube I2. The tube I3serves to control the rate ofenergy flow into the tube I2. The behavior of the modulating impedanceis dependent, in the main, upon a very interesting and useful phenomenonwhich obtains with respect to transmission lines, or equivalentcircuits, whose electrical length is equal to an odd number ofone-eighth wavelengths of the frequency impressed upon them. If anyimpedance which is purely resistive be shunted across one end of theone-eighth wavelength line and its magnitude be varied, the impedanceseen when looking into the other end of the line will appear constant inmagnitude but variable in phase in accordance with variations in themagnitude of the resistance. Wny this obtains will clearly be seen uponreference to the well-known impedance formula for tran-smission lineswhich is here given in its simplified form for the non-dissipative case:

In this relation, Z1 is the impedance observed at one end'of atransmission line whose electrical length is 9, whose characteristicimpedance is Zo, and across the far end of which is shunted an impedanceZz. Now a one-eighth wave-length line will have 9 equal to 45 and, if wemake Zz a pure resistance equal to R, the equation re duces to:

The modulus of this expression si the same for all values of R and isequal in magnitude to the characteristic impedance but varies in phase,as is clearly shown in Fig. 1A. Thus, when R is zero, Z1 .iS purelyinductive; when R is equal to the characteristic impedance of the line,Z1 is resistive; and when R approaches w Z1 tends to become purelycapacitive. Conversely, if an impedance of constant modulus and variablephase were placed at one end of a one-eighth wavelength line, a pureresistance of varying amplitude would be obtained at the other end.

This, in brief, is the function of the line I0 in Fig. l, whoseelectrical length is equal to an odd number of one-eighth wave lengthsat the carrier frequency. A variable resistance must appear shuntedacross the load point 8 in order to obtain the desired amplitudemodulation of the carrier signal supplied to that point. In order thatthis may obtain, the phase of the plate current of the tube I2 is causedto vary with respect u to the carrier frequency 'voltage applied to theplate by means of the transmission line I0. This phase shift may beachieved by applying to the control grid oi the tube I2 a signal ofcarrier frequency which is variable in phase with respect to thatappearing on the plate. One method of accomplishing this is to feed backcarrier frequency current through an impedance whose phase is variable,and impress the resulting voltage on the grid. The phase of the gridvoltage will vary as the phase of the impedance is varied. According tothe system disclosed, it is desired to vary the phase of the gridvoltage independently by means of this impedance but to leave theamplitude unaffected. Hence, the modulus of the variable impedance inthe grid circuit must be constant. Such an impedance may be obtained, asshown in Fig. l, by transforming a variable resistance through a secondone-eighth wavelength line or its equivalent. In the embodiment shown, aresistance whichl varies in response to the modulating signal may be theplate resistance of tube I3 which is transformed to an impedance ofvariable phase and constant modulus by means of the line II, and appearsin the grid circuit of the tube I2. It will, of course, be understoodthat it may be necessary to vary the actual lengths of any or all of thelines to compensate for the fortuitous tube capacities in which thelines are terminated. Furthermore, when operating the system at certainfrequencies, it may be convenient to replace the transmission lines bytheir equivalent circuits comprising lumped reactive elements.

Returning again to the consideration of the modulator tube I2, the chiefproblem is to supply to its grid circuit a current of carrier frequency,the phase of which is the same as that of the voltage applied to theplate. According to theory, this signal should also have variations inamplitude corresponding to those of the plate voltage, but in practiceit has been found that this is not essential and that the signal may bederived at a point in the system at which the departure from this modeof variation is not too great. For example, as shown in theflgure, aline I4 whose electrical length is equal to an integral number plusthree-eighths wave-length of the carrier frequency, has one end coupledto the tank circuit at the point 6 and its other end coupled to the gridof the modulating tube through a resistance I5. This resistance ispreferably large compared to the .combined impedance consisting of thatplaced across the grid by the line II and that of the line I4, so thatthe current through it will be in phase with the carrier signal on theplate of the tube. When this obtains, the voltage applied to the gridwill be in phase with that on the plate when the impedance in the gridcircuit is purely resistive, and will assume a reactive component as thephase of this impedance is varied. The result will be to vary the phaseoi the plate current in the tube with respect to the plate voltage, orto alter the load line upon which the tube operates for various pointsin the modulation cycle.

This is clearly shown in Fig. 1B which shows an idealized triode platefamily, upon which are superimposed the load lines traced for variouspoints in the cycle. For peaks and valleys of modulation, the load linewill be a circle, the only difference between peaks and valleys being inthe direction of traversal of this line which is counter-clockwise forpeaks and clockwise for valleys, as indicated in the diagram. At carrierlevel, the loadline will be straight, as shown,

age applied to the plate of the tube I2.

indicating that the tube dissipates energy like a pure resistance.Intermediate points in the modulating cycle will, of course, correspondto elliptical paths as shown. The location of the load lines withrespect to the characteristics will depend upon the magnitude ofthe'direct volt- It is immediately apparent from the diagram that theminimum plate current swing over a carrier frequency cycle is l 1/5times the peak occurring at mbdulation peaks and valleys, and that thisminimum obtains at carrier level.

Referring now to Fig. 2, there is shown a further embodiment of theinvention. In this instance, the carrier is tapped off at a lowimpedance point on the quarter-wave line I6 which is connected to theplates of the tube the grids of which are supplied with carrier from aconvenientl source. The quarter-wave line I8 inverts the low impedanceof the tank circuit in the same manner as in the previous embodiment.The modulating signal is applied to the grids of the control tubes I9 inparallel, the plates of which are conveniently supplied with D. C. byconnecting them to a Aquarter-wave line 20. The line may be shorted atits far end to which D. C. is supplied, and presents an open circuit atits other end. The plates are coupled to the grids of the modulatingtubes 2| by means of the one-eighth Wave-length line 22. The tubes 2|are supplied with D. C. through the center tap to the choke 23 shuntingthe far end of a one-half wavelength line 24, the near end of which isconnected to the plates of the tubes 2|, and the further function ofwhich will be considered presently. The plates of tubes 2| are alsocoupled to one end of a line 25 whose electrical length is equal toone-eighth wave-length, or an odd number of one-eighth wave-lengths, atthe carrier frequency. The other end of line 25 may be coupled to theload point 26 through an impedance inverting line 21, whose electricallength is equal to a quarter-wave length, or an odd number of quarterwave-lengths, and whose characteristic impedance may be so chosen as 'toprovide the desired impedance across the load point. It will appear thatit will also be desirable to match the impedance of the one-eighthwavelength line 25 to that presented by the tubes 2|. Since theimpedance of the line will, in general, be low, it may be convenient toreverse the positions of the lines, placing the quarter-y waveimpedance-inverter adjacent the tubes and the one-eighth Wave-lengthline adjacent the junction point 26. The operation of the system willnot, in. effect, be altered, and it may be more convenient to match theone-eighth wavelength line to the impedance at the junction point.Hence, the line functions in the capacity of an impedance transformer.

vThe significant feature wherein this embodi-A ment differs from that ofFig. 1 is in the means used to feed back the carrier frequency currentto thegrid circuits of the modulator tubes. This is accomplished bymeans of the pentodes 28 which, because of their high plate impedancesact, when their grids are excited by a voltage of carrier frequency, asgenerators of carrier frequency current, the amplitude of which isindependent of external impedance in their plate circuits. A suitablemeans of exciting the grids of tubes 28 is by means of the one-halfwavelength line 24 from the plates of the modulator tubes 2|. When thismeans is employed, the grid voltage and the plate voltage of themodulator tubes 2| will differ in amplitude by a factor proportional tothe amplitude of the impedance presented by the end of the one-eighthwave-length line 22, and will diifer in phase by the phase angle of thatimpedance. In the present case, since the modulus of the imperiance isconstant, the variation in amplitude of this voltage will correspond tothat of the carrier frequency voltage applied to the plates of the tubes2|. The D. C. voltage applied to tubes 28 must be adjusted properly withrespect to those on the tubes 2| since no blocking condensers have beenprovidedy except at 29 where the plates are connected to the grids ofthe modulator tubes 2|. Plate voltage may be supplied via the shortedquarter-wave line 30; however, it will, of course, be understood thatany of the means for supplying the tubes with the proper voltages may bereplaced by equivalents, and that there is no intention to restrict theinvention to those shown.

The above description of the invention has been limited to theapplication of the novel modulating impedance in a particular modulatingsystem. Furthermore, only one means has been shown for obtaining animpedance of constant modulus but variable phase for inclusion in thegrid circuit of the energy-absorbing tubes. It will, however, beunderstood that my invention is applicable to any system of absorptionmodulation and that equivalent means may be used subject only to therestrictions imposed by the appended claims.

I claim: i

1. In a modulating system; a source of wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means` comprising al controllableenergy-dissipating space discharge device, said space discharge devicehaving at least an anode, a cathode, and a control grid, and having aneffective impedance variable in phase in accordance with the phase ofthe signal applied to its grid for frequencies within said range, meansfor varying the phase of signals within said range in response to acontrol signal, means for deriving from said system a signal havingsubstantially the frequency of said wave energy, means for supplyingsaid derived signal to said phase-varying means, a source of a controlsignal, means for applying said control signal to said phase-varyingmeans to vary the phase of said derived signal, means for applying thesignal whose phase is thus varied to the grid of said space dischargedevice, and means coupling said space discharge device to saidfirst-mentioned source, and adapted to transform the effective impedanceof said space discharge device to an impedance of varying magnitude.

2. In a modulating system; a source of wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal,` said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, and having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid for frequencies Within said range, means for varying the phaseof signals within said range in response to a control signal, meanscoupled to the anode of said space discharge device for deriving asignal having the frequency of said Wave energy, means for supplyingsaid derived signal to said phasevarying means, a source of a controlsignal, means for applying said last-named control signal to saidphase-varying means to vary the phase of said derived signal, means forsupplying the signal whose phase is thus varied to the grid of saidspace discharge device to vary the phase of the effective impedancethereof, and means coupling said space discharge device to saidfirstmentioned source, and adapted to transform the effective impedanceof said space discharge device to an impedance of varying magnitude.

3. In a modulating system; a source of wave energy having a frequencyWithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, and having an effective impedancevariable in phase in accordance With the phase of the signal applied toits grid for frequencies within said range, means for varying the phaseof signals within said range in response to a. control signal, highimpedance space discharge means coupled to the anode of said spacedischange device for deriving a signal having the frequency of said waveenergy, means for supplying said derived signal to said phase-varyingmeans, a source of a control signal, means for applying said last-namedcontrol signal to said phase-varying means to vary the phase of saidderived signal, means for supplying the signal whose phase is thusvaried to the grid of said space discharge device to vary the phase ofthe effective impedance thereof, and means coupling said space dischargedevice to said first-mentioned source, and adapted to transform theeffective impedance of said space discharge device to an impedance ofvarying magnitude.

4. In a modulating system; a source of Wave energy having a frequencywithin a certain frequency range: and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, and having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid for frequencies within said range, means for varying the phaseof signals within said range in response to a control signal, means forderiving from said system a signal having the frequency of said waveenergy, means for shifting the phase of said derived signal by apredetermined fixcd amount, means for applying said derived andphase-shifted signal to said phase-varying means, a source of a controlsignal, means for applying said control signal to said phase-varyingmeans to vary the phase of said derived and phaseshifted signal, mcaLisfor supplying the signal vchosc phase is thus varied to the grid of saidspace discharge device to vary the phase of the effective impedancethereof, and means coupling said space discharge device to saidfirst-mentioned source, and adapted to transform the effective impedanceof said space discharge device to an impedance of varying magnitudo.

5. In a modulating system; a source of wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprisingl a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, and having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid, a source of a signal of varying phase, means for applying saidsignal to the grid of said space discharge device to vary the phase ofthe effective impedance thereof, and means coupling said space dischargedevice to said first-mentioned source, and adapted to transform theeffective impedance of said space discharge device to an impedance ofvarying magnitude.

6. In a modulating system; a source of wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, and having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid, a source of a signal of varying phase, means for applying saidsignal to the grid of said space discharge device to vary the phase ofthe effective impedance thereof, and means coupling said space dischargedevice to said first-mentioned source, said last means comprising atransmission line having an electrical length substantially equal to anodd number of one-eighth wave lengths at a frequency within said range,for transforming the effective impedance of said space discharge deviceto an impedance of varying magnitude.

7. In a modulating system; a source of Wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, and having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid. a source of signal of varying phase, means for applying saidsignal to the grid of said space discharge device to vary the phase ofthe effective impedance thereof, and means coupling said space dischargedevice to said first-mentioned source, said last means comprising animpedance transformer device and an impedance inverter device adaptedcooperatively to change the effective impedance of said space dischargedevice to an inverted impedance of varying magnitude.

8. In a modulating system; a source of wave energy having a frequencywithin a certain frequency range; and means coupled to 'said source forcontrollably dissipating energy from said source inresponse to a controlsignal, said means comprising a controllable energy-dissipating spacedischarge device, said space discharge device having at least an anode,a cathode, and a control grid, and having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid, a source of sigthereof, means forY transforming the effectiveimpedance of said space discharge device to an lmpedance of varyingmagnitude, and impedance inverter means for inverting the impedance thustransformed so as to produce an impedance varying throughout apredetermined range of impedances, said last two means coupling saidspace discharge device to said iirst-mentioned source.

9. In a modulating system; a source of Wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at' least ananode, a cathode, and a control grid, and having an effective impedancevaria-ble in phase in accordance with the phase of the signal applied toits grid, a source of a signal of varying phase, means for applying saidsignal to the grid of said space discharge device to vary the phase ofthe effective impedance thereof, means for inverting the eiiectiveimpedance ol said space discharge device to produce an impedance havinga magnitude Within a predetermined range, and means for transforming theimpedance thus inverted so as to produce an impedance of varyingmagnitude, said last two means coupling said space discharge device' tosaid first-mentioned source.

10. In a modulating system; a source of Wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, sa-id means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, said anode being coupled to saidsource, and said space discharge device havingA an eiiective impedancevariable in phase in accordance with the phase of the signal applied toits grid, a second space discharge device having ananode, a cathode, anda control grid, and having an effective impedance variable in magnitudein accordance with the magnitude of the signal applied to its grid,means coupling said last-named space discharge device to the grid ofsaid flrst space discharge device, said coupling means being adapted totransform the effective impedance of said second spa-ce discharge deviceto an impedance of varying phase, means for deriving from said system asignal having the frequency of said wave energy, .means for applyingsaid signal to the grid of said rst space discharge device, a source ofa control signal of varying magnitude, and means for applying saidcontrol signal to the grid of said second space discharge device to varythe phase of said transformed impedance and thereby to vary the phase ofthe signal applied to the grid of said rst space discharge'device. i

1l. In a modulating system; a source of wave energy having a frequencywithin a certain frequency range; and means coupled to said source forcontrollably dissipating energy from said source in response to acontrol signal, said means comprising a controllable energy-dissipatingspace discharge device, said space discharge device having at least ananode, a cathode, and a control grid, sa-id anode being coupled to saidsource, and said space discharge device having an effective impedancevariable in phase in accordance with the phase of the signal applied toits grid, variable impedance means having the magnitude of its impedancevariable in response to a control signal, means coupling said variableimpedance means to the grid of said space discharge device, saidcoupling mea-ns comprising a transmission line having an electricallength substantially equal to an odd number of one-eighth wave lengthsat a frequency Within said range for transforming said impedancevariable in magnitudeto a-n impedance variable in phase, means forderiving from said system a signal having the frequency of said waveenergy, means for applying said signal to the grid of said spacedischarge device, a source of a control signal, and means for applyingsa-id control signal to said variable impedance means to vary themagnitude of its impedance and thereby to vary the phase of the signalapplied to the grid of said space discharge device.

THOMAS M'. GLUYAS, JR.

